#include <bits/stdc++.h>
using namespace std;
int main() {
  double s;
  cin >> s;

  double dis = 0;
  int step = 0;
  for (double len = 2 ; dis < s; len = len * 0.98) {
    step++;
    dis += len;
  }

  cout << step;

  return 0;
}